Let's face it: you can sometimes forget a password, because well... it happens! I can't help you with all of them, but I can tell you how to recover your lost Linux root password thanks to Tips4Linux. Just follow the below steps to recover it:
Just the other day we were having a discussion on using the root shell in Ubuntu. Now, remember, the root user account is disabled with no assigned password on a default Ubuntu system so administrative tasks need to be done using the
sudo command. For nearly all of the administration you would need
sudo will be adequate. There are occasionally those fringe cases where you might require a root shell. Below I have a few alternatives and then, if you must, the correct way of opening a root shell.
Ubuntu has an excellent security tool called sudo that allows the administrator to delegate control of certain commands to certain users. But to use it you must type the sudo word before any command, and validate (and confirm) it with your system account password. But... some users (like me) wants a more faster solution to become root user simply typing the su command.
In my list of ten tips for KDE 4.0, number 10 was a workaround for the fact that launching an application from the menu that needs to be run as root would cause KDE to refuse your password.
Once you start installing new GTK themes in Ubuntu, you will notice that applications that run as root, such as the Synaptic Package Manager, look unthemed and ugly. This is because although the root user is hidden in Ubuntu, it is still technically a separate user with separate appearance settings.
To fix this, run these three commands in a terminal. They will cause your own theme, font, and icon preferences to always be used by the root user: